Process and apparatus for removing air pollutants from oven-stack emissions

ABSTRACT

A SYSTEM FOR PREVENTING HOT NOXIOUS VAPORS, COMPRISING AEROSOLS OF ORGANIC MATERIALS EMANATING FROM AN OVEN IN A MANUFACTURING PROCESS, FROM POLLUTING THE ATMOSPHERE THROUGH OVEN-STACK EMISSIONS COMPRISES A SPRAY CHAMBER, FINNED COOLING COILS DISPOSED WITHIN THE SPARY CHAMBER, AND A MIST ELIMINATOR COMMUNICATING WITH THE SPRAY CHAMBER. HOT GASES EMANATING FROM THE OVEN ARE COOLED BY THE FINNED COILS TO PROVIDE A TWO-PHASE LIQUID CONDENSATE IN THE SPRAY CHAMBER. THE FINNED COILS ARE SPRAYED BY THE TWO-PHASE CONDENSATE, AT HIGH PRESSURE, TO SCRUB AND CLEAN THE FINNED COILS OF ACCUMULATED TARS AND TO AGGLOMERATE THE AEROSOLS IN THE SPRAY CHAMBER. ANY AEROSOLS EMANATING FROM THE SPRAY CHAMBER ARE FILTERED BY THE MIST ELIMINATOR.

Nov. 9., 1971 N. J. HANDMAN 3,618,301

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Norman J. Handman ByHIs AHorney United States Patent 01 ice 3,618,301PROCESS AND APPARATUS FOR REMOVING AIR POLLUTANTS FROM OVEN-STACKEMISSIONS Norman J. Handman, Cherry Hill, N.J., assignor to ClermontEngineering Company, Incorporated Filed Mar. 11, 1969, Ser. No. 806,155Int. Cl. B01d 47/06 U.S. CI. 55-89 4 Claims ABSTRACT OF THE DISCLOSURE Asystem for preventing hot noxious vapors, comprising aerosols of organicmaterials emanating from an oven in a manufacturing process, frompolluting the atmosphere through oven-stack emissions comprises a spraychamber, finned cooling coils disposed within the spray chamber, and amist eliminator communicating with the spray chamber. Hot gasesemanating from the oven are cooled by the finned coils to provide atwo-phase liquid condensate in the spray chamber. The finned coils aresprayed by the two-phase condensate, at high pressure, to scrub andclean the finned coils of accumulated tars and to agglomerate theaerosols in the spray chamber. Any aerosols emanating from the spraychamber are filtered by the mist eliminator.

BACKGROUND OF INVENTION This invention relates generally to a system forcontrolling air pollution and recovering organic material, and moreparticularly to a process and apparatus for removing air pollutants fromoven-stack emissions. The process and apparatus of the present inventionare particularly useful for removing aerosols from hot oven gasesresulting from a manufacturing process utilizing organic materials, suchas plasticizers and organic mineral siprits, hereinafter referred to asorganics.

It has been proposed to remove noxious hot vapors, including liquid mistparticles (aerosols) of organic materials of about one micron or smallerin diameter, from oven-stack emissions by scrubbing the hot vapors withwater. The prior-art process, however, required large quantities ofwater and presented an unwieldy problem of disposing of the largequantity of contaminated water. Also, the extraction of organics fromsuch large quantities of water was not practical because of the problemspresented in storing the large quantities of water.

SUMMARY OF INVENTION The improved apparatus for removing aerosols oforganic materials from hot oven gases comprises a spray chamberconnected to the oven to receive the hot aerosols, finned cooling coilsdisposed within the spray chamber, and a mist eliminator communicatingwith the spray chamber. The hot oven gases are cooled in the spraychamber by the finned cooling coils, a separate coolant being pumpedthrough the finned coils. The cooled aerosols are condensed as atwo-phase condensate (organicswater) and fall to the bottom of the spraychamber. The finned coils are sprayed with the two-phase condensateunder high pressure to increase the heat transfer efficiency between theaerosols and the cooling coils, to scrub and clean the cooling coils ofany condensed tars thereon, to clean the air stream of any dirt and dustcarried over from the oven gases, and to agglomerate the aerosols intodroplets that fall to the bottom of the spray chamber. Any cooledaerosols remaining in the spray chamber are filtered by the misteliminator. The organic material is recovered from the two-phasecondensate of the spray chamber and from the mist eliminator.

Patented Nov. 9, 1971 BRIEF DESCRIPTION OF THE DRAWING tion andrecovering organics from a process for manufacturing linoleum.

DESCRIPTION OF THE PREFERRED EMBODIMENT The improved apparatus andprocess for preventing noxious vapors from a manufacturing operationfrom polluting the atmosphere will be described in connection with amanufacturing process for making linoleum, for illustrative purposes. Itis, however, within the contemplation of the present invention for theimproved apparatus and process to provide means for removing hot organicaerosols from oven-stack emissions in manufacturing processes whereinthe average diameter of the aerosols is in the order of about one micronor less.

Referring now to the drawing, there is shown an oven 10 of the type usedin the manufacture of linoleum 12 communicating with the input of aspray chamber 14 through a conduit 16 and a valve 18. The output of thespray chamber 14 is connected to the input of a mist eliminator 20through a conduit 22, and the output of the mist eliminator 20communicates with the atmosphere through a conduit 24, such as a stackvented to the atmosphere.

In the manufacture of the linoleum 12, a cloth 30, such as hessianfabric, for example, is passed through the oven 10 by any suitableconveying means such as rollers 32 and 34, for example. Linoleum cement36 from a tank 38 is deposited on the cloth 30 as the cloth 30 entersthe oven 10, the cloth 30 being moved in the direction of the arrow 40.The linoleum cement 36 may comprise oxidized linseed oil mixed withresins, such as kauri gum and fillers which must be cured. Plasticizers,such as dioctyl phthalate and mineral spirits, for example, are added tothe linoleum cement for curing purposes.

Hot air at a temperature of about 350 degrees F. is introduced into theoven 10 through ports 42 to cure the liquid cement 36. During the curingprocess, aerosols, consisting of particles of the organic materials ofthe plasticizers, mineral spirits and resins from the coating 36, areformed within the oven 10. If these aerosols were permitted to passdirectly into the atmosphere through a stack 44 communicating with theoven 10, the atmosphere would become dangerously polluted and present aserious health hazard to humans and animals that would be exposed to it.The aerosols of the organic particles are dispersed in the hot air andother gases, such as carbon dioxide, for example, formed in the oven 10during the manufacturing process.

Means are provided to recover the pollutants, that is, the noxiousvapors (aerosols) from the oven-stack emissions so as to render harmlessthe ultimate emission to the atmosphere. To this end, the hot noxiousaerosols of organics are prevented from being emitted from the stack 44by a closed damper 46, and the hot aerosols are passed into the inlet ofthe spray chamber 14 through the conduit 16 and the open valve 18. Thehot aerosols are passed over a plurality of finned cooling coils 50. Thefinned cooling coils 50 are connected to a source 52 of a coolant at atemperature of about 55 degrees F. through a closed system including apump 54.

The coolant may be any suitable liquid or gas, such as water or ammonia,for example, which may be reused continuously since it does not come incontact with the aerosols and is in a closed system.

Hot aerosols entering the spray chamber 14 at about 350 degrees F. arecooled to between and 70 degrees F. after passing over the finnedcooling coils 50. The hot oven gases passing over the finned coolingcoils 50 cause the plasticizer fumes, solvents, and stream from themoisture in the air to condense and form a two-phase condensate 56,comprising a layer of organics floating on water at the bottom of thespray chamber 14. The two phases of the condensate 56 may form anemulsion.

The condensate 56 is pumped at high pressure to spray nozzles 58 througha conduit 60 and a high pressure pump 62. The nozzles 58 are directedonto opposite sides of the finned cooling coils 50 to increase the heattransfer efficiency between the aerosols and the finned cooling coils50, to scrub and clean the finned cooling coils 50 of any accumulatedtars and resins deposited from the hot vapors, to clean the vapors ofany dirt and dust carried over by the oven gases, and to agglomerate theaerosols into much larger droplets so that they can be trapped easily byeliminators 64 disposed within spray chamber adjacent the outletthereof. To accomplish these functions the pressure of pumping thecondensate 56 should be between about 80 and 100 lbs. per square inch.This pressure is about four or five times that ordinarily used for airconditioning purposes. Also, the spraying of the condensate 56 should befrom opposite sides of the finned cooling coils 50.

About eighty percent of the pollutants, mainly the aerosols, have beenremoved from the oven gases by the time they reach the outlet of thespray chamber 14. The oven gases are now blown to the mist eliminator 20by a blower 66 disposed within the conduit 22 that communicates with theoutlet of the spray chamber 14 and the mist eliminator 20. The misteliminator 20 is preferably one of the type generally known as theBrinks demister type (Monsanto Company) for filtering aerosols of aboutone micron or less in diameter. The gases emanating from the misteliminator 20 and passing through the stack 24 have less than tenpercent of the volatilized organics originally present in the gases inthe oven 10.

The two-phase condensate 56 can be collected in a recovery tank 70through a drain 72 and an open valve 74 communicating with the spraychamber 14 and leading into the recovery tank 70. A drain 76 and an openvalve 78 also communicate with the bottom of the mist eliminator 20 fordraining the condensate from the mist eliminator 20 into the recoverytank 70. Thus, at least ninety percent of the volatile organics thatwould ordinarily pollute the atmosphere, if not recovered, are recoveredby the improved method and apparatus. The recovered organics may bereused in the manufacturing process, thereby providing an economic useof materials.

I claim: 1. In a process of removing air pollutants from ovenstackemissions of the type comprising hot noxious aerosols, said aerosolscomprising particles of organics dispersed in vapors of water and gas,each of said particles having a diameter of about one micron or less,and said aerosols having an initial temperature of about 350 degrees F.,the improvement comprising the steps of cooling said hot aerosols bypassing them over finned cooling coils to form a two-phase condensate ofa first portion thereof comprising water and organics,

spraying said cooling coils with said two-phase condensate with apressure of at least 80 pounds per square inch to agglomerate a secondportion of said aerosols,

blowing the remainder of said aerosols through a mist eliminator tofilter said organics and water therefrom as a two-phase filtrate, and

collecting said two-phase condensate and said twophase filtrate.

2. In a process of removing air pollutants from ovenstack emissions asdescribed in claim 1, said step of cooling said areosols comprises, inaddition,

pumping a coolant in a closed system through said finned cooling coils,said coolant being physically separate from said two-phase condensate.

3. In a process of removing air pollutants from ovenstack emissions asdescribed in claim 2, said step of spray ing said cooling coilscomprising, in addition,

spraying said cooling coils from opposite sides thereof with saidtwo-phase condensate with a pressure of between about eighty and onehundred pounds per square inch.

4. In a system wherein hot noxious aerosols are formed in oven-stackemissions, said aerosols comprising particles of organics dispersed invapors of water and gas, each of said particles having a diameter ofabout one micron or less, and said aerosols having an initialtemperature of about 350 degrees F., improved apparatus for removingsaid aerosols comprising a spray chamber,

conduit means communicating with said oven-stack emissions and saidspray chamber to direct said hot aerosols to said spray chamber,

a plurality of finned cooling coils in said spray chamber,

a closed coolant system including said finned cooling coils for coolingsaid cooling coils with a coolant, whereby to cool and to condense aportion of said aerosols, as a two-phase condensate, in said spraychamber,

spraying means disposed adjacent said cooling coils within said spraychamber, a high-pressure pumping system for pumping said twophasecondensate through said spraying means with a pressure of at leastp.s.i.,

a mist eliminator,

conduit means communicating said spray chamber with said mist eliminatorwhereby to filter, as a two-phase filtrate, any aerosols passing fromsaid spray chamber to said mist eliminator,

said coolant being physically separate from said twophase condensate,whereby said coolant is not contaminated by said two-phase condensate,

said spraying means comprising spray nozzles disposed on opposite sidesof said cooling coils,

said high-pressure pumping system comprising means to agglomerate aportion of said aerosols in said spray chamber and means to clean any ofsaid organics that may stick to said finned cooling coils,

blower means in said conduit means communicating with said misteliminator, whereby to blow aerosols from said spray chamber to saidmist eliminator, and means to separately collect said two-phasecondensate and said two-phase filtrate, whereby to recover saidorganics.

References Cited UNITED STATES PATENTS 682,050 9/1901 .Enben 5580 X692,415 2/1902 Baker 55222 2,147,248 2/1939 Fleisher 5590 X 3,473,29810/1969 Berman 55-222 OTHER REFERENCES Brink, Jr.: Air Pollution Controlwith Fiber Mist Eliminators" from The Canadian Journal of ChemicalEngineering (Reprint), June 1963, pp. 134-138.

REUBEN FRIEDMAN, Primary Examiner C. N. HART, Assistant Examiner U.S.Cl. X.R. 55-259

